Virus-neutralizing monoclonal antibodies against bovine viral diarrhea virus and classical swine fever virus target conformational and linear epitopes on E2 glycoprotein subdomains.

The envelope glycoprotein E2 of pestiviruses plays a crucial role in viral entry and elicits a virus-neutralizing humoral immune response. Consequently, the epitopes recognized by monoclonal antibodies (mAbs) on E2 are a significant focus in pestivirus research and diagnostics. In this study, we characterized a panel of murine mAbs against the E2 protein of classical swine fever virus (CSFV) and bovine viral diarrhea virus (BVDV), two major pathogens for swine and cattle, respectively. The majority of mAbs neutralized the virus in vitro and recognized conformational epitopes, which were also detected by sera from infected animals. Notably, binding to these epitopes was retained after low-pH treatment, although conformational epitopes were disrupted upon disulfide bond reduction. The epitopes of the anti-CSFV mAbs were located in various domains of E2, including the interdomain linker sequences. Conversely, all but one of the anti-BVDV mAb epitopes were located in domain A. Moreover, the reactivity of one mAb suggests a conformational interdependence among the linker sequences of pestivirus E2. The panel of mAbs characterized in this study holds potential to support basic research on the mechanism of early pestivirus invasion and to assist in the design of E2-based diagnostic tools and vaccines.

Importance: Classical swine fever virus (CSFV) and bovine viral diarrhea virus (BVDV), which belong to the family Flaviviridae, cause economically significant diseases in pigs and cattle. The pestivirus glycoprotein E2 is located on the viral surface and is targeted by antibodies that neutralize virus infection. Due to its variability, E2 is a useful antigen for the development of diagnostic tests to differentiate between infections caused by different pestiviruses. In the present study, two panels of monoclonal antibodies (mAbs) specifically reactive with either CSFV or BVDV E2 were characterized. Interestingly, the majority of mAbs neutralized the respective virus in vitro. Epitope mapping revealed that the mAbs recognized low-pH-resistant epitopes of conformational nature located in different domains of CSFV E2 (anti-CSFV mAbs) or in domain A of BVDV E2 (anti-BVDV mAbs). The recombinant proteins along with the characterized mAbs have the potential to develop improved pestivirus-specific diagnostic tests and vaccines.